Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.53	8.716%	$200.6136	$200.61	$200.60	$200.60
Purchase #2	$228.94	6.430%	$243.6608	$243.66	$243.65	$243.70
Purchase #3	$241.46	12.216%	$270.9568	$270.96	$270.95	$271.00
Purchase #4	$66.86	8.832%	$72.7651	$72.77	$72.75	$72.80
Purchase #5	$15.54	12.436%	$17.4726	$17.47	$17.45	$17.50
Purchase #6	$43.47	7.785%	$46.8541	$46.85	$46.85	$46.90
Purchase #7	$147.36	13.673%	$167.5085	$167.51	$167.50	$167.50
7 purchase totals =	$928.16		$1,019.8315	$1,019.83	$1,019.75	$1,020.00